I have a odd coloured not a coloured so no pics but I can tell you what to wear.
Ridden classes- Tweed jacket, blue or cream shirt with a tie and tie pin, navy blue velvet hat with flesh coloured straps, hair in bun with hairnet, beige or canary jophhurs, long black leather boots, brown gloves and cane.
Inhand classes- Tweed jacket, blue or cream shirt with tie and tie pin, a hat (it doesn't have to be a riding hat), smart trousers light coloured if your horse has dark legs and dark if your horse has light legs (but no black), smart shoes that you can run in and brown gloves and cane.
This is a photo from my very first show with my coloured cob
He's in a simple inhand bridle with leather lead. I'm wearing blue hat, blue shirt with red tie, tweed jacket with blue velvet collar, dark trousers (as his legs are white) and brown jodphur boots. Also brown gloves and cane.
As long as you look neat and tidy you should be fine, the main part is enjoying it and as you get out and about, you'll pick up what you need and how to do things